The present invention relates to mechanical and chemical-mechanical planarization of microelectronic substrates. More particularly, the present invention relates to processing media having a planarizing surface to planarize a microelectronic substrate and a separate finishing surface to clean the microelectronic substrate after planarization.
Mechanical and chemical-mechanical planarization processes remove material from the surfaces of semiconductor wafers, field emission displays and many other microelectronic substrates to form a flat surface at a desired elevation. FIG. 1 schematically illustrates a planarizing machine 10 with a platen or base 20, a carrier assembly 30, a planarizing medium 40, and a planarizing liquid 44 on the planarizing medium 40. The planarizing machine 10 may also have an under-pad 25 attached to an upper surface 22 of the platen 20 for supporting the planarizing medium 40. In many planarizing machines, a drive assembly 26 rotates (arrow A) and/or reciprocates (arrow B) the platen 20 to move the planarizing medium 40 during planarization.
The carrier assembly 30 controls and protects a substrate 12 during planarization. The carrier assembly 30 generally has a substrate holder 32 with a pad 34 that holds the substrate 12 via suction. A drive assembly 36 of the carrier assembly 30 typically rotates and/or translates the substrate holder 32 (arrows C and D, respectively). The substrate holder 32, however, may be a weighted free-floating disk (not shown) that slides over the planarizing medium 40.
The planarizing medium 40 and the planarizing liquid 44 may separately, or in combination, define a polishing environment that mechanically and/or chemically-mechanically removes material from the surface of the substrate 12. The planarizing medium 40 may be a conventional polishing pad composed of a polymeric material (e.g., polyurethane) without abrasive particles, or it may be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. In a typical application, the planarizing liquid 44 may be a chemical-mechanical planarization slurry with abrasive particles and chemicals for use with a conventional nonabrasive polishing pad. In other applications, the planarizing liquid 44 may be a chemical solution without abrasive particles for use with an abrasive polishing pad.
To planarize the substrate 12 with the planarizing machine 10, the carrier assembly 30 presses the substrate 12 against a planarizing surface 42 of the planarizing medium 40 in the presence of the planarizing liquid 44. The platen 20 and/or the substrate holder 32 then move relative to one another to translate the substrate 12 across the planarizing surface 42. As a result, the abrasive particles and/or the chemicals in the polishing environment remove material from the surface of the substrate 12.
Planarizing processes must consistently and accurately produce a uniformly planar surface on the substrate to enable precise fabrication of circuits and photo-patterns. As the density of integrated circuits increases, the uniformity and planarity of the substrate surface is becoming increasingly important because it is difficult to form sub-micron features or photo-patterns to within a tolerance of approximately 0.1 xcexcm on non-uniform substrate surfaces. Thus, planarizing processes must create a highly uniform, planar surface on the substrate.
To obtain a highly uniform substrate surface, conventional planarizing processes generally involve two separate cycles: (1) a planarizing cycle in which material is abraded and/or etched from the substrate with a primary planarizing medium and a planarizing liquid as set forth above; and (2) a finishing cycle in which very small defects are smoothed-out and waste particles are cleaned from the substrate surface with a secondary finishing medium and an appropriate cleaning fluid (e.g., deionized water). The primary planarizing medium used during the initial planarizing cycle may be a firm polyurethane polishing pad with holes or grooves designed to transport a portion of the planarizing liquid below the substrate surface. The polishing pad may alternatively be an abrasive polishing pad with abrasive particles fixedly bonded to a suspension material. The secondary finishing medium used during the finishing cycle may be a soft, compressible material with a napped fiber surface. For example, the finishing medium may be a compressible, nonabrasive polyurethane pad with a napped surface.
The two separate cycles of conventional planarizing processes are generally performed at two separate work-stations of a single planarizing machine or on two separate machines. For example, a first work-station of a typical planarizing machine has a first platen supporting the primary planarizing medium, and a second work-station has a second platen supporting the secondary finishing medium. In the operation of the planarizing machine 10 shown in FIG. 1, the substrate holder 32 initially picks up the substrate 12 from an external stack of substrates (not shown), and then the carrier assembly 30 positions the substrate 12 on the primary planarizing medium 40 of the first work-station to commence the planarizing cycle. After the planarizing cycle has finished, the carrier assembly 30 moves the substrate 12 to the finishing medium (not shown) at the second work-station (not shown). For example, the finishing medium is typically mounted to a second platen (not shown) that moves the finishing medium as a nozzle (not shown) sprays deionized water near the substrate to clean the substrate surface. After the finishing cycle is over, the carrier assembly 30 places the substrate 12 in a measuring machine (not shown) to measure the thickness of particular layers on the substrate. This two-cycle process is then repeated with a new wafer.
In the competitive semiconductor and microelectronic device manufacturing industries, it is desirable to maximize the throughput of finished substrates. One drawback of conventional two-cycle planarizing processes, however, is that the time between the planarizing and finishing cycles reduces the throughput. For example, because conventional planarizing machines have separate planarizing and finishing media at separate work-stations, it typically takes 5-10 seconds to transfer the substrate from the planarizing medium to the finishing medium. Although a 5-10 second delay may not seem important, it results in a significant amount of down-time in large scale operations that manufacture devices on several thousand substrates each year and planarize each substrate several times. Accordingly, it would be desirable to reduce the down-time between the planarizing and finishing cycles.
Another drawback of conventional two-cycle planarization processes is that the finishing cycle increases the time of the overall process for each substrate. In conventional processes, the planarizing cycle typically runs for approximately 60-300 seconds, and the conditioning cycle typically runs for approximately 30-60 seconds. Because the substrate carrier sequentially positions the substrate on the planarizing media and then the finishing media, the planarizing media remains idle during the finishing cycle. The entire finishing cycle, therefore, is down-time for the planarizing medium. Thus, it would be desirable to develop a more efficient process and apparatus for performing the planarizing and finishing cycles.
Still another drawback of conventional two-cycle planarization processes is that the planarizing machines must have two separate work-stations. For example, the conventional planarizing machine described above has two separate platens for individually controlling the planarizing and finishing media. As such, conventional two-station planarizing machines may have duplicative components that do not enhance the throughput of finished substrates.
The present invention is a method and apparatus for mechanically and/or chemical-mechanically planarizing and cleaning microelectronic substrates. In one embodiment, a processing medium for planarizing and finishing a microelectronic substrate has a planarizing section with a first body composed of a first material and a finishing section with a second body composed of a second material. The first body may have a relatively firm planarizing surface to engage the substrate, and the first body supports abrasive particles at the planarizing surface to remove material from the substrate during a planarizing cycle. The second body may have a relatively soft buffing or finishing surface to clean the abrasive particles and other matter from the substrate during a finishing cycle. The planarizing and finishing sections may be fixedly attached to a backing film, or they may be attached to one another along abutting edges with or without the backing film.
In one particular embodiment, the processing media may be an elongated web configured to extend between a supply roller and a take-up roller of a web-format planarizing machine. The planarizing and finishing sections of this embodiment may be long strips of material extending lengthwise along a longitudinal axis of the web. In another embodiment, the planarizing and finishing sections may be coupled to a backing film in alternating transverse strips so that the abutting edges extend along a widthwise dimension of the web. As such, there may be a plurality of different sections or zones upon which the microelectronic substrates may be planarized and cleaned.